Fix win unit tests broken at 9778206.

Windows uses the system implementation of itoa which goes
to 36.

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1285433002 .
diff --git a/core/src/fxcrt/fx_system_unittest.cpp b/core/src/fxcrt/fx_system_unittest.cpp
index ae1e41c..e1a986e 100644
--- a/core/src/fxcrt/fx_system_unittest.cpp
+++ b/core/src/fxcrt/fx_system_unittest.cpp
@@ -73,7 +73,11 @@
 TEST(fxcrt, FXSYS_itoa_InvalidRadix) {
   FX_CHAR buf[32];
 
-  FXSYS_itoa(42, buf, 17);
+#if _FXM_PLATFORM_ != _FXM_PLATFORM_WINDOWS_
+  FXSYS_itoa(42, buf, 17);  // Ours stops at 16.
+#else
+  FXSYS_itoa(42, buf, 37);  // Theirs goes up to 36.
+#endif
   EXPECT_EQ(std::string(""), buf);
 
   FXSYS_itoa(42, buf, 1);
@@ -114,7 +118,11 @@
 TEST(fxcrt, FXSYS_i64toa_InvalidRadix) {
   FX_CHAR buf[32];
 
-  FXSYS_i64toa(42, buf, 17);
+#if _FXM_PLATFORM_ != _FXM_PLATFORM_WINDOWS_
+  FXSYS_i64toa(42, buf, 17);  // Ours stops at 16.
+#else
+  FXSYS_i64toa(42, buf, 37);  // Theirs goes up to 36.
+#endif
   EXPECT_EQ(std::string(""), buf);
 
   FXSYS_i64toa(42, buf, 1);